1. Field of the Invention
The present invention relates generally to a control system which controls operation of automotive devices, such as an internal combustion engine and/or accessories thereof. More specifically, the invention relates to a control system for automotive devices which are associated with a vehicular slip control, such as a traction control for adjusting driving torque to be distributed to a vehicular driving wheel for preventing the driving wheel from causing excessive wheel slip.
2. Description of the Background Art
In recent years, traction control systems have been developed and proposed for optimizing vehicular driving performance and for better vehicle driving stability by preventing driving wheels from causing excessive slippage. Such traction control systems have been realized by advanced technologies in microprocessors having substantially high speed in data processing. For example, one of typical traction control systems has been proposed in Japanese Patent First (unexamined) Publication (Tokkai) Showa 62-150034. The disclosed traction control system includes an auxiliary throttle valve in an air induction system for performing adjustment of induction air in traction control. The auxiliary throttle valve is associated with a throttle servo mechanism which is controlled by a control unit performing traction control in response to wheel slippage. Namely, when wheel slippage occurs, the control unit becomes active to reduce the opening angle of the auxiliary throttle valve to reduce intake air flow rate and whereby reduce the engine output torque to suppress wheel slippage at driving wheels.
In general, such traction control systems are effective for optimizing vehicle driving performance and for providing satisfactory vehicle driving stability.
On the other hand, the traction control systems in the prior art have been so designed as to perform slip or traction control operation independently of other control, such as engine control, engine accessory control and so forth. This tends to cause mis-matching of control to cause degradation of the performance of various automotive devices, such as the internal combustion engine, the engine accessories and so forth. For example, knock suppressive spark ignition timing control for the internal combustion engine is performed independently of the traction control. Therefore, when a knocking suppression mode spark advance retarding operation is performed while traction control is active, the engine driving torque is fluctuated from a target value by spark advance retarding operation. This causes error in both of the traction control and the spark ignition timing control. Similarly, in case of an air/fuel ratio control in the automotive internal combustion engine, though acceleration enrichement is disabled, feedback control for maintaining the oxygen concentration in an engine exhaust gas at a stoichiometric value. This causes an abnormal value in the oxygen concentration indicative feedback signal. This causes a overrich or an overlean air/fuel mixture in the engine cylinder.
In case of an automotive air conditioning system, ON/OFF control of an engine driven compressor in the air conditioning system has been performed independently of the traction control. Therefore, the engine driven compressor can turn ON or OFF during traction control to vary the engine load. Variation of the engine load causes variation of engine output torque to cause error in the traction control.